346 THE INVERTEBRATA 



as an adult organ, the antennary gland being functional in the adult 

 only in certain of the Malacostraca. In the Ostracoda and Leptostraca 

 both are vestigial in the adult. Each of these glands (Figs. 229-231) 

 has an end sac and a duct leading from the end sac to the exterior. The 

 end sac is always mesodermal and doubtless represents a vestige of 

 the coelom. The duct is sometimes (in the Malacostraca probably 



^sac. 



Fig. 229. The maxillary gland of Estheria. After Cannon, sac. end sac. 



Fig. 230. Diagrams of the antennal gland of the early metanauplius of 

 Estheria. After Cannon. A, The whole gland. B, The sphincter in section. 

 duct, intracellular ectodermal duct; ect. ectoderm; sac. end sac (coelomic); 

 sph. sphincter cells. 



always) a multicellular, mesodermal structure, and sometimes intra- 

 cellular and of ectodermal origin. At the junction of end sac and duct 

 there is often a sphincter. The antennal gland of the Decapoda is 

 usually very complicated. That of the crayfish lacks extensions of the 

 bladder which lie among the viscera in many other genera, as in crabs. 

 All the parts of the organs are excretory, and the function of the 



